1. Field of the Invention
The present invention relates to the field of semiconductor fabrication. More specifically, the present invention relates to a nozzle assembly for delivery of a liquid (for example, photoresist) for use in semiconductor fabrication.
2. Background of Related Art
One of the apparatuses used in the fabrication of semiconductors is a spin track which deposits a certain amount of chemicals onto a wafer (such as photoresist) during manufacturing. Wafers proceed through the spin track, and a certain amount of photoresist (a photo sensitive chemical used to transfer circuit features from a mask to the wafer), is deposited upon the wafer. The wafer is then spun to make an even coating of the liquid applied across the surface of the wafer. Then, the wafers proceed through remaining steps in the manufacturing process to process the wafer and form the integrated circuit or other device. Several steps are involved in manufacturing a semiconductor in this fashion. However, significant periods of time lapse between when a first batch is run through the spin track machine, and a subsequent batch is run. In addition to resist, such machines are also used for depositing other chemicals including polyimide.
Because a substantial period of time may elapse between when one batch of wafers is run through the machine and a subsequent batch, there are times when the machine remains idle. If more than ten minutes elapse between batches, the remaining fluid in the nozzle portion of the apparatus starts to dry causing a residue to build up in the outlet of the dispensing tube. Once the remaining fluid at the end of the dispense tube has started to dry, a cleaning procedure is required in order to ensure that the fluid is evenly dispensed and no particles contaminate the wafers being processed. One prior art method for removing dried photoresist from the dispensing tube is to inject a solvent into the dispensing tube to remove any dried resist. Then, "dummy wafers" are run through the spin track apparatus and liquid is dispensed so that the solvent injected into the dispensing tube is purged. The dummy wafers are refused after cleaning for the next time that the resist needs to be removed from the apparatus. A considerable amount of labor, equipment, and materials is consumed by this cleaning process.
Yet another prior art approach is a swing arm dispensing tube. The swing arm is moved over a solvent drain and the liquid is dispensed through the tube until all the dried residue has been removed from the fluid path. This approach is effective, however, because chemicals such as photoresist are very expensive and a large quantity is typically required to purge all the remaining dried resist in the dispensing tube, this is an expensive solution.
Yet another problem with prior art methods is that the dispensing tubes tend to be bent, and thus become off center from the optimum position from which the chemical is to be dispensed. An off center dispensing nozzle from the optimum fluid deposition center is directly related to material yield loss.
In addition, prior art dispensing tubes have the tendency to migrate fluid to the flat surface of the dispense tube. The fluid dries and can cause particulate contamination to the subsequent wafers.